This is written in the instructions (for the All American) :Yes, the 2-3 inches of water are absolutely necessary and should be put into the canner before canning begins. I tend to add a little more- closer to 5-6 inches just to be on the safe side (this will depend on how tall your jars are though). Sometimes lots of water remains, and other times there is very little left.
No definitely do not open the canner when it has any pressure in it, only when it's on zero pressure and no more pressure comes out when you remove the weight. There could be a nasty accident if you try to open the canner when there's pressure in it!
I think what it means is, when you have finished a batch of canning, you have taken out your jars and you want to use your canner to do another batch then you will need to refill the water to the desired level again as water is lost during the process.
Did your canner come with a manual? If so, I'd suggest sticking to it as closely as possible for safety! My canner is by Presto and the manual has been so helpful. This is also a good description of the process from start to finish.
You can buy it separately, then gently melt it and pour it into the jars, making sure to try and get air bubbles out afterwards. This lady has a good video, you can also just use a normal butter knife.
Use Adequate Liquid / Water
It is critical to understand the importance of having enough water in the cooker in use. During cooking or canning, you should use 2 to 3 inches of hot water in the bottom of the canner before you place the filled jars on the rack. Water level must be maintained during the canning process. Check the water level between batches. Please read the recipes or canning instructions. You must never allow the pressure cooker to boil dry. If there is not enough water in the pressure cooker and it boils dry, the unit will be ruined, cannot be repaired, and must be replaced.
In your opinion, is lard beneficial to the canned meet in the jar on some way ?
Also, do you sterilize jars before canning (meat, vegetables) ?
Thank you a lot, and I really do not plan to open the canner while the process is ongoing.