Call for help (Gardener's) please!

Photo clears it up yes?! Its clearly a.....??!!

Evening all of you! I need help. Especially as it were from the gardeners among you. I've been wandering around the damp grass with my wellies on and a cup of tea in my hand studiously examining all the plants. While I've figured out (the blooms in summer gave them away) my roses and lilies and the pear tree and apple tree also gave themselves away last year I still have a couple of plants & trees which are currently nameless. When we moved the lady we bought the house from assured us the twenty foot tree which grew up the balcony and above the house was indeed a fruit tree but she wasn't too sure which fruit. She thought it might be something between an apricot and a peach. Last year it didn't fruit….How on earth, without digging it up and taking it to the garden centre, would I find out exactly what it is? Gazing up at in wellies for a year has not produced any inkling as to what it might be!

Next bit of help (can you tell I've been storing these up?) my glass in my greenhouse blew out with all our fierce and rather damp weather and while I’m dreaming of summer I suspect I must fix this fairly soon. Plastic perhaps? We have a local cat who keeps trying to bolt through the glass when it sees Daisy bound about in the garden and I feel plastic might be a little more forgiving then glass as it tries to escape?