When can you cycle MTG?

Cycling can be used at instant speed. Abilities can be used at instant speed by default, and sorcery timing restrictions have to be printed on the card or be in the rules/reminder text for that permanents abilities.

Does cycling count as discarding?

Cycling is an ability youll find on all kinds of cards, from creatures to lands to enchantments. If you pay a cards cycling cost, rather than cast it or play it as you normally would, you discard it and draw a new card instead.

Is cycling at instant speed?

Cycling can be used at instant speed. Abilities can be used at instant speed by default, and sorcery timing restrictions have to be printed on the card or be in the rules/reminder text for that permanents abilities.