RE question ?

My cyybertech is almost 400 but my Character lvl is only 44. When i get to 400 can i start to re lvl 50 armors and mods for the change of schematics and molecular stabilizers ?

techinically, you can be like lvl 12, and be a 400 cybertech and can craft all the level 49 stuff.

but can you craft the lvl 50 stuff and re the lvl 50 stuff ?

Yes, your combat level has no impact on your Crew Skills, only your actual skill level. If the item requires a skill of 400 in your skill to craft it, it will also require a skill of 400 to RE it.

By the way, having a combat level 50 toon who has a craft that requires Scavenging makes it simple to get a decent crafter for the other professions that require Scavenging as well but keep them at a low combat level. My first 50 was 400 Cybertech, 400 Scavenging and 400 Underworld Trading. That meant I could either go out and harvest Scavenging nodes or run Scavenging missions to get the mats to level up an Armstech and an Armormech without having them ever leave fleet once they hit level 25 and got the ability to send out three crew members on missions or crafting sessions. (Of course, that meant choosing classes that got two companions and the ship droid by the time you hit Nar Shaddaa, so one was a Smugger, the other a Trooper.) The Underworld Trading on my Cybertech also got any advanced mats my Armormech needed. I'd just use my 50 to farm the green quality metals and compounds and run missions for fluxes that the other two crafters needed to level, and both of them hit 400 in their craft before they hit combat level 30. In fact, my Armormech is still only level 28, but from my other crafters I was able to fund running Scavenging and Underworld Trading missions so that he's 400-400-400 on his crew skills already.

i have a low level character with 400 cybertech and the game doesn't allow me to put level 50 mods in items. so i can't remove them to re them. do i have to be a level 50 character?

yes I am a lv 10 Sin with 400 Cyber tech and 400 UT and Scavenging. I can not put higher level mods into attachment gears because of level restrictions. No matter if its bound or not the skill wont matter unless you have the needed level. But you can RE any attachment if you have that proper skill leveled.

You need a 50 and some legacy-bound shells to circumvent that restriction, yes.