I would appreciate it if you could reply my question early.

[NLT]

Can anyone help me on the following. Which sentence is correct?

1.I would appreciate it if you could reply my question early.
2.I would appreciate it if you can reply my question early.
3.I would appreciate if you could reply my question early.
4.I would appreciate if you can reply my question early.

[mykwyner]

I would say number 1. with the addition of the following change: "...could reply to my question..." Reply is an intransitive verb. It cannot take a direct object.

[MikeNewYork]

Can anyone help me on the following. Which sentence is correct?

1.I would appreciate it if you could reply my question early.
2.I would appreciate it if you can reply my question early.
3.I would appreciate if you could reply my question early.
4.I would appreciate if you can reply my question early.

None of them.

1. is the best, but it needs a "to" after "reply".

[riverkid]

Can anyone help me on the following. Which sentence is correct?
1.I would appreciate it if you could reply my question early.
2.I would appreciate it if you can reply my question early.
3.I would appreciate if you could reply my question early.
4.I would appreciate if you can reply my question early.

NLT,

Your use of 'early' sounds like it may be a direct translation from your own language. In English we don't use 'early' like this.

We use 'reply quickly'; 'as quickly/fast as possible'; 'quickly reply'; as soon as possible; asap