1. Japanese industry was severely lacking in capacity. Once the need was actually realised, as the Japanese focused in elan and discipline to carry the day rather than superior firepower (which worked very well when facing unprepared or less well equipped enemies, which they did early in the Pacific War), it was far too late.

2. The Japanese had some interesting rocket technology and were experimenting with jet engines when the war ended. However, they did not have the resources for grand projects such as the V2 and especially an atomic bomb. One should note that the US invested MASSIVE resources into the Manhattan project, which had more than 100 000 employees for several years, nearly unlimited resources, the best physicists from all over the world (that had fled from occupied countries or Germany itself, from allied countries and the US itself).

3. The Japanese suffered from a combination of inter-arms services rivalry and a lack of resources. For example, both the army and the navy developed a 13,2mm AA gun - a different one for each service. Those guns could not use the same ammunition. Japense tank development was based off French ww1 designs and British early inter-war tankette designs and barely got any better as the war progressed. Pacific islands is not tank terrain anyway. The Japanese copied western designs in many cases (and in some cases made copies better than the original).

The Type 3 machinegun was based on the French Hotchkiss 1914.

The Type 92 was an upscaled and belt-fed improved Type 3.

The Type 96 was based on the Czechoslovak ZB vz.26 (also known as MG 26(t) in German service, Kulsprutegevär m/39 in Swedish service, M30 in Romanian service and Bren in British service).

In regards to your second question, the Japanese had their own rocket-power kamikaze aircraft, the Yokosuka MXY7 Ohka, although it wasn't nearly as advanced as the V-2.

Why did the Japanese military lack a semi-automatic rifle during the war? The U.S had the Garand, the Germans had the Gewehr 41, and the Soviets the SVT and SVS-36. However I did see they copied the M1 Garand. However only 250 were made. What took them so long to develop one?

Most of the World used Bolt Actions, Germany made 15 Bolt Action Rifles for every Gewehr 41 and STG-44, the Soviets production of the SVT stopped in 1942, most rifle men were armed with the Nagant at all stages of the war.

It is not strange at all that the Japanese would keep their Bolt Actions, they were the Rifle of choice for the day. Most powers used them only or primarily.

Lastly how much did the Japanese spend researching weapon technology? It seems most of the known weapons of the army (type 99 machine gun and type 100 sub-machine gun) did not enter service until the beginning of the war.

This was a continual problem with Japan, unlike Germany they were slow to adopt to the enemies tactics, discard their own failed tactics (like Banzai charges) or create counter tactics.

That Type 100, they only made about 10-20 thousand of them for an army six million at its height. A very limited production run for weapon that had proven vital and was especially apt for they terrain they were fighting on. Another such weapon they lacked was a mass produced anti weapon like the Panzerfaust or Bazooka, another necessity since their main anti tank artillery was a 47mm cannon until the end of the war.

Closer to the end of the war the Japanese tried to play catch up after their industrial base had been wrecked. Early in the war they tended not to innovate even when in their best interest.

Japan rcieved a number of german (notably the me 163 and me262) resulting in the Nakajima Kikka and Mitsubishi J8M. These did not enter widespread service.

One of the more succesful japanese fighters was powered by a licence built Dialmer Benz db601 powerplant. This made it one of the only Japanese fighter powered by a liquid cooled inline engine.

Other late war Japanese designs where on par with the best the allies had to offer (Ki 84 and the N1K1) but these where never produced in large enough numbers and experienced/ quality pilots where in extremely short supply.

Japan's relative lack of mineral wealth, lower population, and recent industrialization meant that their weapons were never produced on the same scale or to the same quality as American weapons. Japan went to war completely industrially unprepared, and it showed; Japan's successes early in the war owed more to extreme aggressiveness of ordinary Japanese soldiers and the under-preparedness of their enemies. Japan's military was designed to fight against the Nationalist Chinese, who were nowhere near as well-equipped as contemporary American and other Western forces, and once the war broke out Japan found itself cut off from foreign supply (for example, in 1939 over 90% of Japan's oil was imported from the U.S.).

Furthermore, the Japanese military was built along different lines to Western militaries. In the 1930s it was themed along Western lines, with the same kind of light tanks, strike aircraft, and mobile machine-gun units as were often seen in European armies at the time, but the Japanese were unique in that their soldiers were expected to overcome difficulties or deficiencies by willpower rather than complaining to their higher-ups, and that loss of life in battle was something to be admired, not avoided; so it didn't really matter if their troops were outgunned. Furthermore, this meant there was little feedback, and so Japan's armies had a "make-do" nature to them, especially in the field of combat engineering. This made them tactically flexible but weak in drawn-out engagements.

The greatest weakness of the Japanese soldier was the poor state of his supply chain, rather than his equipment, as training made Japanese troops extremely aggressive, to the point of being able to overcome being outgunned. Japan lacked good transport networks and had an antiquated rail system, as well as choosing to fight in terrain that often lacked good supply networks. Japan was not a "high-tech" power in the 1930s. Its industry was still in its infancy when the war broke out; many of its military projects (e.g., light machine-guns, rifle ammunition, submarines, aircraft carriers, and battleships) had been started under the supervision of British, Italian and German advisers.