1. **`Is the kanji form of the verb to play (a stringed or keyboard instrument)?`**
Yes. {} is the correct kanji for playing keyboards, and stringed instruments.
And you should say
> {}{}{}{}?
for any musical instrument.
However probably not correct usage though, I often use
{}{}? "Do you play some instruments?"
for any musical instruments like even drums, flutes, etc.
2. **`If the answer to Q1 is yes, why is it conjugated ?`**
> a) {}{}?
It implies "Do you usually play any musical instruments?" or "Do you want to play/try any musical instruments? (Probably at music shop)"
> b) {}{}?
It implies "Can you usually play any musical instruments?" As you quote, it is talking about the ability to play instruments.
3. **`Does one read the first kanji as {} or as {}?`**
{}is a colloquial form of {}. So you can shorten the sentence to **{}{}?** to form the heavy metal band.