4 stroke engines aren't newer than 2 stroke engines, they're simply different in how they operate. Each have their advantages and disadvantages for various uses.

The type of engine you use depends mainly on the type of plane, so decide on that first.

.46 is referring to cubic inches, yes - so approx 7.65cc.

Do some research into gas engine basics (RC or not), it will help a lot if you understand how internal combustion engines work.