In simple, no. If you did not register it before 01/01/14 then once more, no. Threaded barrels on pistols are illegal and defined as "assualt weapons". Even the little 22lr Ruger Mark with a threaded barrel is now an "assualt weapon" in CT.
Now for your pre-ban question. If you purchase a pre-ban it must be of the first ban type, before Sept. 14, 1994. Only then could you purchase it and have a threaded barrel on it.
Still, even if you have this Pre Ban Glock with a threaded barrel, you still would need to follow the "assualt weapons" laws here in CT. Its defined as an "assualt weapon", so its very well likely you will not be able to carry it with the threaded barrel.
You could find out if the Glock is a pre ban by calling Glock. Last I heard from people in CT, Glock is getting flooded by the influx of calls, finding if their Glcok is a pre-ban. So they might tell you send an email.
Sound suppressors are legal to purchase and to own in CT. You will need to submit form, pay the tax, and the wait till you get the ok. Right now in CT its six months to a year.
Side note for you - you must still have a ten round magazine for it.