To get prism sword at chang ban be liu bei and defeat cao ren he will arrive as rienforcments after your first or second move if it is not cao ren then just kill the rienforcments on the top path after you win the sword will "call" liu bei
Sword of shu: on the battle of cheng du. I think you have to be liu bei (see liu bei cheat) save pang tong and go straight for mian zhu gate via the forest.
You will be ambushed kill the three ambush units and go for mian zhu gate after a while ma chao and another officer will appear. If you saved pang tong the other officer will be blocked from reaching the gate.
If you defeat the officers in front of mian zhu gate it will open and liu zhang will appear do not fight instead go back and rescue zhuge liang. After a while liu zhang will surrender and you will get sword of shu.
Sky scorcher: simple but difficult. As wei defeat lu bu and you should recieve the weapon believe me extremely hard to beat
Liu bei: to get liu bei defeat shu musou mode
Cao cao: to get cao cao defeat wei musou mode
Sun jian: to get sun jian defeat wu musou mode
The reason I put them in there is so you can get the best character in the game
Yes you can get lu bu: to get lu bu win all three musou modes then pick one of the three (sun jian, cao cao or liu bei) and win musou mode with them lu bu will be unlocked
Well I hope this helped I will submit more when I find it out maybe I will write a faq.