-C or C++. For that you will need Ndless on your calculator. Then go learn one of these languages and read the Ndless SDK docs. You can always ask questions here if you need help.
-What you code is what you get
-Same
-Same

Welcome to Omnimaga by the way !

Huh ? That's weird.

5656: Number correction (true story)
5657: You are known as the geek (true story)
5658: Whenever there is a comp problem you get asked (true story)

5661 : You second 5657 and 5658. (True story)
5662 : You scream when you drop your calc (true story)
5663 : People press random keys on it while you code (true story)
5664 : You give 'em a good kick in the butt (true story)
5665 : PALINDROME !!! You get it before Pimathbrainiac. (True story)
5666 : True story (true story)

Well a model dedicated to hacking around has already been suggested to TI, they just won't. TI's business model is understandable but they won't accept that some people like programming something just because it's labeled "calculator". Or rather they give them limited consideration with the half locked-down z80 series which is a power dwarf compared to the Nspire or the new HP Prime.
Cheap handheld devices that you can program directly do not exist. Fully open ones even less. DIY ones do but it's not for everyone. Calcs are a nice compromise as you already have them for school, and most people here started programming with these.
Just my two cents. We will never agree with TI and community alternatives have all failed up until now, so we are turning to the concurrence which is more tolerant and community friendly than TI. The Casio PRIZM and HP Prime are good examples : neither officially supports native code but the first has no restrictions on it while HP doesn't seem to react to our current attempts to hack the Prime (whose hardware is fully documented and open to arbitrary flashing, giving us complete control of it).

Yup, nice to see you back. I hope you stick around.

You can check bit 7 of port $02 then. Also you need to manually put the calc in 15 MHz mode if you want it.