Re: why can i send picture text messages to some iPhones but not others?
There's a basic incompatibility with SMS/MMS between Apple and the rest of the world - Apple doesn't use the industry standard. They're working on making it compatible, but until they get there, there's only one thing you can try. Have your iPhone friends send you an iMessage as a text message, not as an iMessage. One message each should set their iMessage app to send and receive properly to and from your number. If that doesn't work, you'll just have to wait until Apple gets its act together, or find an app that comes in both iOS and Android that you and your friends can use.
(You're lucky. Ten years ago, you couldn't send MMS between different carriers. It took about 2 years to get that one straightened out. And everyone was using the industry standard, the messages just seemed to get lost.)