This has been discussed on MSO. The accepted answer is as follows:

Cross posting is fine, provided:

1. You respect the differences in the audiences at the different sites;

2. You allow some time to pass between successive questions, and update them in the light of the answers previously received; and
   

3. Really the first point again, you should have an idea what the new site offers in terms of expertise to crack your question that the previous site did not.
   

Usenet-style forum spamming is, I hardly need to say, bad.

So asking the same thing is fine, but exact copy-pasting may not be appropriate, you should at least try to tailor it to the site.

As far as migrating, If a question is on-topic on a site, it is not migrated even if it would be on-topic on another site.

This has been discussed on MSO. The accepted answer is as follows:

Cross posting is fine, provided:

1. You respect the differences in the audiences at the different sites;

2. You allow some time to pass between successive questions, and update them in the light of the answers previously received; and
   

3. Really the first point again, you should have an idea what the new site offers in terms of expertise to crack your question that the previous site did not.
   

Usenet-style forum spamming is, I hardly need to say, bad.

So asking the same thing is fine, but exact copy-pasting may not be appropriate, you should at least try to tailor it to the site.

As far as migrating, If a question is on-topic on a site, it is not migrated even if it would be on-topic on another site.

This has been discussed on MSO. The accepted answer is as follows:

Cross posting is fine, provided:

1. You respect the differences in the audiences at the different sites;

2. You allow some time to pass between successive questions, and update them in the light of the answers previously received; and
   

3. Really the first point again, you should have an idea what the new site offers in terms of expertise to crack your question that the previous site did not.
   

Usenet-style forum spamming is, I hardly need to say, bad.

So asking the same thing is fine, but exact copy-pasting may not be appropriate, you should at least try to tailor it to the site.

As far as migrating, If a question is on-topic on a site, it is not migrated even if it would be on-topic on another site.

This has been discussed on MSO. The accepted answer is as follows:

Cross posting is fine, provided:

1. You respect the differences in the audiences at the different sites;

2. You allow some time to pass between successive questions, and update them in the light of the answers previously received; and
   

3. Really the first point again, you should have an idea what the new site offers in terms of expertise to crack your question that the previous site did not.
   

Usenet-style forum spamming is, I hardly need to say, bad.

So asking the same thing is fine, but exact copy-pasting may not be appropriate, you should at least try to tailor it to the site.

As far as migrating, If a question is on-topic on a site, it is not migrated even if it would be on-topic on another site.