yes sideshoots will continue to be productive for the life of the plant, though smaller. lettuce will self sow if you have the space to let it. Some years I was tempted, but cut it back after a few weeks because the tall stalks leaned over and I wanted the space for new tender plants since lettuce seeds are cheap. in the fall I let some go to seed and didn't mind. I spread mulch and though have plenty of parsley seedlings only one lettuce out of it. Perhaps I cut them too quickly. You could leave one plant & remove the others. Mark it with a chopstick or plant label because you may forget or another family member may help you by cutting it down. :o) It's usually me who does the snipping, so I need reminders to myself.

What kind of tomato plants you have there? Chances are you will get more blooms and tomatoes as long as you can keep the critters out. Your tomatoes are still pretty small and they look very healthy from the photo, so if they are well watered and fed they will definitely bloom and give you more fruits. In general tomatoes will stop setting fruits when enough fruits are already set and growing. Once ripe fruits are picked (or in your case unripe ones), new buds will set. Be hopeful!! Good fall crops include salad greens, Asian greens, any kind of brassica (broccoli, kale), beets, carrots, turnips, arugula. Really you have a wide selection there. You have to decide what you want to eat and grow.

Fall is THE time to plant! (When do you think the garden centers might catch on to this?) I buy things all summer (lots on clearance sales) and keep them in pots and plant in the fall. Easier on the plants and easier on me! There is so much garden work to do in the spring, especially if you plant vegtables or (bite my tongue) a-a-annuals. Also if you are as disorganized as I am you can't remember what is coming up where in the spring, so by digging to plant something new, you risk killing plants that are late to come up. Technically brandon7 said it all in his informative post. But sometimes my enthusiasm gets the best of me and I can't resist putting my 2 cents in. ;-)

Depends on where you are located, your climate, your soil temperatures. Lettuce won't even germinate in hot soil much less grow to bolt. Where I am there will be no more lettuce planting until mid-September. If you have a heavily shaded area then some varieties are a bit more heat tolerant once they are established but you still have to get them to germinate first so you may have to do that indoors. Dave.