Arduino code update

Remote start arduino code update 2 1. I noticed a problem on the code: if I send a comand (like 'start') and I do not wait to be done and send another command (like 'temperature') the last command do nothing, and the sms remain on SIM card memory. - the command that erase the SMS in the slot should be replace with a command to delete all sms. - Optional: can you write the code in a way that in the same time it execute a command (like 'start') it can execute other commands (like 'Voltage', 'temperature') even if will do it after the first command, before it will be done? (Maybe not using delay, but millis? ) 2. Any other SMS received, but not the commands in the code should reply a SMS ('Bad command') 3. Add a function that will send a SMS ('low battery') if the Voltage drops under a certain value (11.5V), but it should be send only once each time the voltage drops from 12V to 11.5V 4. I want to replace the SIM800l module with SIM7600E module. I am not sure if the commands are different for this module (I didn't try it yet), but if they are we have to update. UPDATE: I set up the SIM7600E module and send SMS, receive SMS and get the sender number. I will send you the code I tried to get the commands. I set up the board to start after boot so we don't need to setup the power pin. 5. Send a SMS "Running for 20 minutes" after "Started" sent SMS (1st attempt or 2nd attempt) after 20 minutes. The SMS will be sent to two phone numbers(declared in the code) - for this task and for the optional one from point 1 do you think an RTC module will help? 6. I want to add a function to check the network signal intensity. A sms command "Network" will return a sms with signal percent. I will send you an arduino code that I used to check the signal and it worked well with SIM800L. (It is a command which return the signal from 0 to 31, and this should be transformed into percent value (100/31*measured value)) 7. Every SMS command on the code should be executed only if received from 3 certain numbers, but if a sms will be received from another number, that SMS should be erased for memory saving reason.