You only need the SIM card installed to send text messages and make calls + cellular data via a phone number.
Otherwise you can just use the phone as is on Wi-Fi just you can't do the above until you have a sim card installed.
While they look similar most of the time the size of the battery is different and will not fit. You better look for the same model battery.
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'''Edit: '''After researching both those batteries. It looks like they both use the same battery and it's the same battery capacity. You should be able to use those batteries vice-versa as they are basically the same.
You only need the SIM card installed to send text messages and make calls + cellular data via a phone number.
Otherwise you can just use the phone as is on Wi-Fi just you can't do the above until you have a sim card installed.
While they look similar most of the time the size of the battery is different and will not fit. You better look for the same model battery.