File LCA or H1b before 60 day grace period ends

USA H1B Visa
1

  1. During the 60 day grace period after employment is terminated, what is the last day the candidate’s LCA can be filed ?

  2. Assume the LCA gets filed on 55th day and H1B on 65th day, is there any violation ?

  3. If the candidate files for F-1 visa on 50th day and then goes to school or keeps looking for job, it is a valid scenario?

  4. Once any employer files H1B after F1 has been filed, can the F-1 visa petition be withdrawn?