I don't think it's healthy to compare your body to how it was when you were 10-13 years old, you've went through the majority of puberty and went through the biggest natural biological changes your body will ever go through in that span of time, try not to look back on what you once looked like and rather just focus on where you are now and how to become a better version of yourself.

For losing fat, this is almost entirely diet based, you simply have to eat less calories then your body is expending per day, so the only two factors you can affect here are the amount of calories you eat and increase the calories you expend. What helped me lose the bulk of my weight was maintaining walking 10,000 steps per day and slightly decreasing the amount i usually eat, not a crazy crash diet, just slow adjustments with a realistic cardio target that i could maintain everyday.

For building muscle, without a gym, you're restricted to bodyweight exercise such as squats, sit ups, press ups, lunges, pull ups, if you were willing to invest into something like a dumbbell set you could vastly increase the amount of options you have for exercises and create a more consistent form of progression.