The Garmin Connect app is free and does most of what you want it to do. Plenty of websites available where you can download GPX for free, amend routes (including start-point, direction etc). Some demand a subscription, but most are free for basic features and you only have to pay for advanced options.
If you don’t wear a heartrate monitor then it won’t measure heartrate. If you don’t tell it how much you weigh then it won’t be able to calculate calorie consumption. Just load the gpx and tell it to start navigation or navigate to the start of the route. Just ignore the stats that you’re not interested in.