[MUMmer-help] MUMmer SNP output data help

[<ra...@bi...>]

Hi all,
I have been working with Iontorrent platform. I have sequence of a bacteria which was obtained by denovo assembly on Ion torrent platform. I have to use this data as a reference for calling SNP's across 6 samples. So it would be draft genome vs draft genome. I have used the nucmer snp caller. My questions are:
1) can i use this tool for calling SNP's from data generated from Iontorrent platform?
2) Do i need to align the draft sequences first before going to the SNP calling option?
2) Should i cal SNP's from one sample and then compare it with others or all the sample's data can be combined and called for SNP's? for example can i go with command line 
nucmer --prefix=ref_qry ref.fasta sample1.fasta sample2.fasta sample.3.fasta
3) IS there an option to generate unique SNP's to a particular sample and common variants across all the samples?
Thanks in advance,
 
Ramya.