The first thing to remember is that there are a lot of muslims, muslim sympathisers and anti-American traitors out there who want us to believe their ridiculous 9/11 consp-theory, so don't get suckered in by them.
Like I said earlier, Al-Q ADMITTED doing 9/11, and they've NEVER said "We didn't do it" so that clinches it for me..
To answer your points-
1- If bombs had gone off in the basements the towers would have collapsed like a house of cards, but what we saw was the steel strusses giving way on the floors where the planes had gone in because the flames from the burning fuel had melted them. That caused the floors above to come crashing down and crush the floors below in a concertina effect.
There's a saying in the building industry- "Never trust a truss", because if the trusses on one floor go, the whole lot above go too.
Below- stills from a TV science documentary showing how the W-shaped trusses melted and gave way-
2- When one of the planes hit WTC2, some of the wreckage went straight through and hit buildings below such as WTC7 which then also collapsed.
3- The Pennsylvania and Pentagon planes disintegrated and / or vapourised.
4- Muslims had already tried to blow up the WTC north tower with a truck bomb in 1993, it killed 6 people including a pregnant woman.
They'd also been committing terrorism all around the world for years before 9/11, so America didn't need to stage a 9/11 false flag as an excuse to invade the mideast, because they ALREADY HAD plenty of good excuses to go kick muslim ass..