[HELP] Simple Call Forwarding using Dial

This is a repost of the same topic on Asterisk General forum. I couldn’t move it here so I had to post a new one instead.

I am a total newbie in asterisk so forgive my simple questions.

I would like to use asterisk for simple call forwarding and I think I can make it happen using Dial application. Here is the deal,

I do have 3 landlines and I want to configure it in a way that whenever Line 1 rings, two calls are made simultaneously (one GSM and one other landline) and gets bridged the one thats picked up first. In addition to that there should be a phone connected to line 1 and if that phone is picked up before the two other lines (Line 2 and Line 3), it should be connected and other dials should be terminated.
And the very last requirement is to make sure the caller did not notice what is going on. I do not want the ringtone of the caller to stop, or alter the tone.

So do I want a lot? Is it possible to hook up such a system?

Here is what I thought, I dont know if it works or not.

I think I need to buy a 4 port TDM card with 3 FXO (for the landlines) and 1 FXS module (for the phone). And I found out that I can add up more than 1 destination to Dial application and its great.
So I guess I will have to add 3 destinations on Dial. smt like,

where Dahdi/3 is actually the FXS port connected to the phone.

Is that configuration correct?

Even if its correct I don’t have a clue if the ringtone of the caller gets affected while those stuff is going behind. It is very important for me to do this without the caller noticing any difference.

It is probably easier just to try. However, having more than one destination inhibits the Dial application from passing through call progress, so the caller should be unaware of the fact that there are three parallel calls.