In a flashback before she left for Alaska, we see Liz turn Agnes over to Scottie. Agnes was born circa spring 2016. Liz went into a coma circa November 2017, and was in a coma for about 10 months, placing her awakening circa September 2018. Presuming she had 6 months of rehab before leaving, this would make Agnes around 3. The child playing her in this scene was clearly several years older than that. Agnes was in fact played here by 3 different actresses, with one of them listed as Agnes at age 2.
Liz goes to the store looking for an "L14-20" male plug electrical plug for the generator. In the prior scenes, it had stopped running, which is usually caused by it running out of gas. An L14-20 is a plug that is used to connect the generator to the home, it has nothing to do with the generator running.