Doesnt matter if he is an adult or not, you cant buy a RIF without a UKARA.... unless youre asking if you can just buy a two tone? thought that was fairly obvious...
Can we please stop putting this kind of erroneous information out there? UKARA is not some sort of 'license' to buy or own a realistic imitation firearm; you absolutely
do not need a UKARA to buy a RIF, UKARA is merely a convenient way for a retailer to establish that you have a reason for buying a RIF, so in the absence of you having a UKARA number, all you actually need is the ability to prove that you have
a legitimate reason for wanting to own one, nothing more. And even this is not part of the law, it is simply so that if you subsequently flip out and rob a bank with your RIF, or indulge in some other nefarious deed with it, the shop which sold it to you can legitimately claim that they sold it to you with good reason, thus removing the possibility of them being prosecuted for aiding you in the crime, because the Act of Parliament which covers this matter is the Violent Crimes
Reduction Act, i.e. it is intended to reduce the likelihood of, and the means to acquire the necessary equipment to, commit a violent crime. If you can convince a retailer that you have some other legitimate reason for wanting to purchase a RIF, one which would also provide them with a suitable line of defence should the police subsequently question the retailer on why they sold a RIF to someone, then they will sell you a RIF without you having a UKARA number. If this was not the case, then you'd have special effects departments, prop buyers, museums etc having to send some member of staff to three airsoft events just so they could go about their legitimate business. Yes, UKARA is a convenient system for airsofters and retailers, but it is in no way the law, nor is it the only means by which you can prove your legitimate reason for wanting to purchase a RIF.
So if I walked into an airsoft shop and showed them my ID for Soho Editors - which is the movie CGI post production special effects company I work for - and told them that I needed a realistic looking M60 machine gun so I could show the effects department at Pinewood Studios how to CGI muzzle flashes, an ammo belt feeding shells, and the empty cases ejecting, from a machine gun for the Vietnam War Movie they were making, then that absolutely is a legitimate reason for wanting to buy and own a RIF and that reasoning also covers me for spray painting toy guns black, moulding rubber prop guns etc, etc, because I have a genuine and legitimate reason for doing so, and this is regardless of the fact that I do have a UKARA number. The Violent Crimes Reduction Act goes into some detail on this matter, giving specific examples of legitimacy, such as the aforementioned movie and theatre production, museum work, historical re-enactments, educational purposes, etc. Similarly, if you go to an airsoft site regularly, the staff there will know you, so if they have a shop at their site, they would likely sell you a RIF regardless of whether you had applied for a UKARA number or not, because they would be able to prove that you are an airsofter simply by virtue of you having attended their site numerous times, and would have a record of you having done so.
UKARA is not a licence, is not a part of the UK's legislation on firearms, is not compulsory for airsofters, is not even mentioned anywhere in the VCR Act - since it came into being after the VCR Act - and is absolutely not a requirement for anyone who owns or wants to own a replica/realistic looking imitation firearm. If it was, you would be applying for it at a Police Station and not at some airsoft site or airsoft shop. It probably is worth getting a UKARA registration if you are an airsofter simply for the convenience of confirming your legitimacy to a retailer, especially if you want to buy from abroad, but that is merely a convenience and is in no way mandatory.