You'll need to do some research to learn about the proper care and feeding of a BSA B25/Triumph TR25.
For instance, yes it's a four stroke and the fluids that should be in it are: Gasoline in the gas tank, fork oil in the forks, Oil in the oil tank, gear lube in the gearbox and some type of lube (some run ATF, some a monograde oil) in the primary chain case.
It's a dry sump motor and normally the oil over long storage will migrate from the tank to the sump of the motor. There's a plate there that you can remove to drain the sump. Make sure you do this before even thinking about trying to start it.
Get a manual
and read it. Read it again and then a third time. There are various ones available. Check with the suppliers on the forum ads and do a little googling. Google "Rupert Ratio" for instance.
What I'm trying to gently point out to you is that is that a lot of your basic questions will be more than answered by doing these things and more importantly, the more you learn, the more you will be able to make decisions about what to do to and what to put in YOUR bike, because they are all different and we all have different needs for them.
We'll be here to give advice for the things that you don't understand or are confused about.... and there will be these things.