you 可以申请EB绿卡, no matter you are employed or not, no matter what status you are in and no matter you are in US or have ever been in US.
When (or whether at all) to LC based 申请绿卡 is the decision of your employer, whether it needs to depend on 工作签证批下来/must work for n years first,... or not, it's also a decision of the employer.
Immigration law places no limitation on any of this.