The red light is the infra-red "eye". It allows it to connect to other Tamagotchis.
Because I have no skill in creating guides, I've compiled the icons and what they do. Also, the left button (A button) selects stuff, the middle (B button) confirms, and the right (C button) cancels, or does close-ups when nothing is highlighted.
Icon 1: The status screen. Shows your Username, character stats, training, age, weight, character, generation, and money.
Icon 2: Food. Meals tame hunger, while snacks make them happy, at the cost of raising their weight.
Icon 3: Toilet. Pretty self explanatory. Selecting this icon when the Tamagotchi's about to poop will raise it's training by 3.
Icon 4: Door. Here, you can play games (lowers weight and raises happiness) buy food or remodel your home, go to the park (raises friendship) or use the PC. (Website's gone, too bad.)
Icon 5: Figure. You can play games, use items, or eat exotic foods if you have a specific figure.
Icon 6: Discipline. Time Out is when your character calls you despite having full stats, and praise is when it breaks down and starts crying. Successfully using these functions raises training.
Icon 7: Medicine. Use when your Tamagotchi is sick, has a toothache, or has become fat.
Icon 8: Connect. Tamagos can only connect with V5s, Music Stars, or themselves. No V1s - V4.5s.
Icon 9: Friends and Memory. Memory is parents or dead Tamagotchis, and Friends are those you connected with.
Icon 10: Attention. You can't select it. It becomes highlighted when it needs you or calls for no reason.
Friendship and Training are different from Hunger and Happiness. Training changes how nice your Tamagotchi will be to others (lower = more prone to be rude to other Tamagotchis) and allows it to be potty trained in the Tamago. Friendship is basically it's life meter. If it's empty, it's more prone to die.
I hope this helped?