1. Did I work illigelly in company B for almost 3 months?
-Obviously, USCIS has made the mistake in your H1 approval. You were legal to work for the last couple of months, but now you may need to stop working until you fix it.
2. Do I need to talk to HR about this?
-Yes. You need to talk to your Human resources this mistake and ask them to contact USCIS to fix it as soon as possible (maybe just need to go to USCIS local office to do that).
3. Can I continue to work in company B if HR will not find the error?
-No, you need this mistake fixed and then, continue your work.
-Obviously, USCIS has made the mistake in your H1 approval. You were legal to work for the last couple of months, but now you may need to stop working until you fix it.
2. Do I need to talk to HR about this?
-Yes. You need to talk to your Human resources this mistake and ask them to contact USCIS to fix it as soon as possible (maybe just need to go to USCIS local office to do that).
3. Can I continue to work in company B if HR will not find the error?
-No, you need this mistake fixed and then, continue your work.