Glycine brings together everything from the first two levels: a small skeleton, an amine, and a carboxyl group whose hydrogen is mobile. Note that the zwitterion gives the same answer — it has the same number of protons.
A variable exercise. What you write is compared with what the InChI engine generates for the same structure, with 3 hints if you want them.
Convert a structure to its InChI and InChIKey and back, convert a whole CSV, XLSX or SDF file, learn how the identifier is derived, and practise writing its layers. The InChI engine is WebAssembly running in your browser, so the tool needs JavaScript — and nothing you open ever leaves your machine.