Chandra's first ability is not a mana ability. It uses the stack and players can respond to it.

You pay all costs and follow all timing rules for cards played with the permission granted by Chandra's first ability. For example, if the exiled card is a land card, you may play it only during your main phase while the stack is empty.

The token created by Chandra's second ability copies exactly what was printed on the original creature and nothing else, with the listed exceptions (unless that creature is copying something else or is a token; see below). It doesn't copy whether that creature is tapped or untapped, whether it has any counters on it or Auras and Equipment attached to it, or any non-copy effects that have changed its power, toughness, types, color, or so on. If it is a Vehicle, it is not crewed.

If the copied creature is a token, the token that's created copies the original characteristics of that token as stated by the effect that created the token, with the listed exceptions.

If the copied creature is copying something else, then the token enters as whatever that creature copied, with the listed exceptions.

Any enters abilities of the copied creature will trigger when the token enters. Any "as [this permanent] enters" or "[this permanent] enters with" abilities of the copied creature will also work.

You choose the targets and how damage will be divided as you activate Chandra's last ability. Each chosen target must receive at least 1 damage.

If some of the targets of Chandra's last ability become illegal, the original division of damage still applies, but the damage that would have been dealt to illegal targets isn't dealt at all.